An ongoing investigation into Prince's death has uncovered counterfeit drugs that actually contained dangerous opiod fentanyl.

A source close to the investigation tells AP that many pills were falsely labelled as Watson 385 while they contained fentanyl, an opioid 50 times more powerful than heroin.

The pills were taken from Prince's estate in Paisley Park after his death in April. What isn't clear yet is if the bottles were mislabelled or had been put in the bottles by Prince himself.

The pills were found in his room as well as in bottles of vitamin C and aspirin hidden inside a suitcase that Prince often travelled with. This is consistent with the autopsy results that showed Prince died of an accidental fentanyl overdose.

The unnamed official says it's likely Prince took the fatal dose sometime in the hours before his death.